Photoelectric machine tool control



July 26, 1938. T. H. LONG 2,125,074

PHOTOELECTRIC MACHINE TOOL CONTROL Original Filed 001:. 19, 1932 4 Sheets-Sheet 1 figz flya 1 1 4.

WITNESSES: INVENTOR 7770/720 H Lang.

ATTORNEY MEW July 26, 1938. 'r. H. LONG PHOTOELECTRIC MACHINE TOOL CONTROL Original Filed Oct. 19, 1932 4 Sheets-Sheet 2 73 INVENTOR 777072705 hf Lory.

74 BY I ATTORNEY July 26, 1938. 'r. H. LONG PHOTOELECTRIC MACHINE TOOL CONTROL Original Filed Oct 19, 1952 4 Sheets-Sheet 5 mm m0 M w m T M my ATTORNEY July 26, 1938. T, H, LONG 2,125,074

PHOTOELECTRIC MACHINE TOOL CONTROL Original Filed Oct. 19, 1932 4 Sheets-Sheet 4 INVENTOR WITNESSES;

' 772077205 f/ Lang.

W BY. m V M f.

. ATTORNEY Patented July 26, 1938 UNITED STATES 2,125,074 PHOTOELECTRIC MACHINE TOOL CONTROL Thomas H. Long, Wakeeney, Kans., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Original application October 19, 1932, Serial No.

Divided and this application October 30, 1935, Serial No. 47,459

15 Claims.

My invention relates to photo-sensitive control systems for machine tools, and constitutes a division of my pending application filed October-19, 1932, Serial No. 638,579, and entitled Photo-sensitive devices.

A control system for an automatic machine constructed and operated in accordance with the teachings of the prior art of which I am aware in general includes a support for a work-piece that is to be shaped in a predetermined manner, a support for a tool that is to engage the workpiece to shape it, and a plurality of motors for moving the tool in the directions required for shaping the work-piece. The motor is controlled by the cooperation of a template that is ordinarily shaped in a manner to correspond to the desired configuration of the work-piece and a mechanical pick-up element which is coupled to the control elements of the motor and which mechanically engages the template in such manner that the motor controls are properly operated to move the tool support in the manner desired.

A consideration of the systems provided in accordance with the teachings of the prior art at .once discloses a number of disadvantages which are inherent in these systems. Among these, the

most important probably involves the difiiculty of suitable coupling the motor controls with the template through the mechanical pick-up. By reason of the difficulty encountered in this connection, the control system is comparatively complicated and involves a large number of accurately machined levers and switches that are apt-to render the operation of the system uncertain and to decrease its accuracy.

Another matter which is ordinarily encountered in the operation of automatic machines of the prior art involves the sluggishness of operation of the mechanical pick-up and the difliculty of providing a suitable pick-up and so adjusting its coaction with the template that the tool accurately and quickly'follows the template in responding to the pick-up.

It is accordingly an object of my invention to provide a control system for an automatic machine in which the cutting tool shall accurately follow the response of the pick-up to the variations in the contours of the template, and by the application of which it shall be possible to shape a work-piece accurately in accordance with desired specifications.

Another object of my invention is to provide a control system for an automatic machine in which the control elements for the motor and the system whereby these elements are coupled to the template shall be of simple and tractable structure.

A further object of my invention is to provide for an automatic machine a control system incorporating a pickup that shall be incrtialess, and that shall be capable of being coupled to the control elements for the motors, whereby the tools are operated, in a simple manner.

A still further object of my invention is to provide for an automatic machine a control system incorporating a pick-up that shall be so tractable as to be capable of adaptation to the operation of'tools of widely diverse dimensions.

One other object of my invention is to provide an optical'systcm to be utilized in the control system of an automatic machine, that shall be of such character that by a simple adjustment thereof the system shall be adapted to be utilized with tools of any. desired dimensions.

Another object of my invention is to provide a photo-sensitive pick-up for the control system of an automatic machine of a type that shall be capable of vfacile adaptation for tools of diiferent characteristics.

Still another object of my invention is to provide a control system for an automatic machine of the type incorporating a pick-up element and a template cooperating therewith in which the template shall be capable of utilization as a finish gauge for the Work shaped in the machine.

A further object of my invention is to provide an optical system for the photo-sensitive control element of an automatic machine of a type wherein, by a single operation of a control knob, the apparatus shall be adapted to operate with a cutting tool of any desired dimensions.

An additional object of my invention is to provide for the adjustable photo-sensitive pickup of an'automatic machine a simple indicating device.

Still another object of my invention is to provide for the adjustable photo-sensitive pick-up of an automatic machine a contrivance whereby the proper indications of the adjustment made by the operator shall be exhibited without any operation on the part of the operator beyond those necessary in the ordinary operation of the machine More concisely stated, it is an object of my invention to provide a control system for an automatic machine that shall be of comparatively simple structure, that shall be capable of accurately and with facility following templates having a wide variety of configurations and that shall be capable of adaptations to use with cutting tools of a wide variety oi diflerent characteristics.

According to my invention, I provide a control system for an automatic machine in which the pick-up element comprises a source oi. radiant energy that cooperates with an optical system to project a radiant image on the contours of a template and a photo-sensitive device to respond to the resultant radiant energy emitted by the template. To avoid the inaccuracies which might arise when the radiant beam traverses the corners and turns of the template, the radiant image projected on the template is of dimensions substantially equal to the dimensions of the cutting edge of the cutting tool. Since the cutting edge of the tool normally has the contour of a circular arc, the image is also circular and is of a diameter equal to the diameter of the cutting edge of thetool.

The apparatus for producing the radiant beam utilized in the practice 01' my invention comprises a source of radiant energy, suchas an ordinary lamp, an aperture plate which is so disposed as to be illuminated by the source and a projecting lens which is so positioned relative to the aperture plate as to cast an. image of the aperture plate on the template. Since it is desirable that the control system be adapted to be utilized with tools having a wide variety of dimensions, the image of the aperture in the aperture plate which is projected on the template is capable of variations in dimensions. The dimensions of the are varied by an adjustment whereby the imaging lens and the aperture and lamp assembly are moved relative to each other and to the template.

To further widen the field of applicability of the pick-up device, a number of aperture plates having apertures of diflerent dimensions are pro vided. Each aperture plate comprises a rectangular slab near the four corners of which a plurality of supporting holes are bored. Between these holes four apertures 01 different dimensions are bored. The lamp is so mounted relative to the support provided for the aperture plate that when the aperture is mounted in any one of the four orientations in which it is capable of being mounted, an aperture corresponding to the particular mounting isilluminated, and is, therefore, imaged on the template.

In the practice of my invention, three aperture plates are generally provided. Each aperture plate is equipped with four apertures which are of diameters that are simple multiples of each other. In practice I prefer that the diameters of the larger apertures oif any one plate should be respectively two, tour and eight times the diameter oi the smallest aperture. The apertures oi the diflerent plates are so related to each other that the total range of tool dimensions is subdivided into a series of overlapping regions, each region corresponding to the image dimensions that can be obtained with a single aperture by varying the optical system over its whole range. Specifically, the ratio of the diameters of corresponding holes of two plates is as the nth root of u is to 1 where n is the number of plates and v is the ratio of successive aperture diameters in any one plate. Thus in the present case the ratio is 8:2:1.

The contrivance whereby the dimensions of the image projected on the template are varied comprises a hand knob which is coupled to the supports for the imaging lens'and lamp and aperture, insuch manner that by simple rotation thereof these elements are moved relative to each other. A circular plate having a plurality of dial indications thereon is mounted concentric with the knob and rotates therewith. The dial scales are three in number, each corresponding to the largest aperture of an aperture plate. Given the indication for any particular setting of the knob, the dimensions 01 the corresponding image may therefore be calculated from a knowledge oi the particular aperture of an aperture plate that is utilized.

The aperture plates are equipped with grooves which are so disposed that when two 01 the aperture plates are mounted in position they cover the scales which correspond to them, leaving open to view the scale which corresponds to the aper- I ture plate mounted in operative position.

The radiations projected across the contour of the template impinge on the sensitive element of a photo-sensitive device. A toothed disc is rotated in the path of the beam and as it rotates it produces a predetermined number of interruptions in the beam. The interruptions thus produced result in pulsations in the output of the photo-sensitive device subjected to the beam and render the output of the photo-sensitive device capable of amplification by an amplifier of the alternating-current type. The output of the amplifier is impressed between the control electrodes and the principal electrodes of a plurality of gasfilled electric-discharge devices of the grid-controlled type, in such manner as to energize the devices in accordance with the magnitude of the output.

The electric-discharge devices are so connected as to excite the relays whereby the clutches, for coupling the driving motors to the proper gears to motivate the tool support in the desired directions, are rendered operative. The system involving the clutches does not concern the present invention, and for this reason, is not described herein. However, it is shown and described in a copending application, Serial No. 659,120, filed March 1, 1933, to O. G. Rutemiller and myself.

The apparatus whereby the radiant beam is produced and the photo-sensitive device are so mounted as to move with the tool support, while the templet is fixed. When the optical elements are so positioned relative to the template that the template completely obstructs the beam the electric discharge devices are deenergized and the particular clutch in operative relation with the motor produces a motion of the tool support such that the tool moves normally towards the workpiece. Aiter the optical elements have been displaced a distance dependent on' the character of the template and a predetermined minimum amount of radiant energy projects over the edge of the template, one set of electric-discharge de-- vices is energized, and a relay is excited to operate a system of clutches whereby any previous motion is interrupted and a traversing motion is initiated. The traversing motion continues until the radiant beam is again obstructed, or the fiux impinging on the photo-sensitive device is moved to a predetermined value, in which case the traversing motion is interrupted and inward or outward motion depending on the condition of excitation of the photo-sensitive device is initiated.

The outward motion is produced when the excitation of the photo-sensitive device is increased to the predetermined value greater than the value for which the traverse motion takes place. In

such a case a second set of electric-discharge devices become energized. When this set of electric-discharge devices becomes energized a system' of relays is energized to operatethe necessary clutches to interrupt the traverse motion and initiate the outward feeding motion.

A third set of electric-discharge devices is provided for the purpose of stopping the entire system when an excess of light impinges on the photo-sensitive device. Such a situation occurs, for example, when the template has by some inadvertence been removed from its proper position, in which case, it is desirable that -the tool and .the machine should be stopped.

It will be noted that the gas-filled electricdischarge devices utilized in the practice of my invention are connected in pairs. This arrangement is essential by reason of the fact that gas-filled devices of the grid-controlled type have what has been designated as a drift characteristic. It has been found that after a gas-filled electricdischarge device has been utilized for some time its properties change in such manner that its potential-response characteristic is varied, that is to say, a gas-filled electric-discharge device at a particular time becomes energized for a certain circuiting distribution of potential between its electrodes. After it has been utilized for a comparatively long period of time, its response characteristic is varied and it becomes energized for another limiting distribution of potential between the electrodes which may be and generally is considerably different from the first distribution.

If a single electric-discharge device were utilized for each actuation of the clutches in the practice of my invention, the drift characteristic might occasion considerable difliculty in view of the fact that when the electric-discharge device changes in any manner, its response to the excitation of the photo-sensitive device might change, and for this reason, the system might respond to the excitation of the photo-sensitive device in a manner contrary to expectation. Thus the inward motion of the tool might be initiated when the traverse motion should continue or the traverse motion might be initiated when the outward motion should continue. To eliminate this difficulty, the system utilized in the practice of my invention is provided with pairs of electricdischarge devices. One device is utilized only for the purpose of initially responding to the condition of the electric-discharge device, and is immediately thereafter deenergized. However, before it is deenergized, it causes the second device to become energized and to produce the necessary excitation of the controlling relays. The range of variation of potential which is impressed by the excitation of the first electric-discharge device on the electrodes of the second electricdischarge device is of sufficient magnitude to produce the necessary changes in the second electricdischarge device, regardless of the drift characteristic.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Figure 1 is a view in perspective showing the essential elements of a control system for a maoptical system constructed in accordance with my invention;

Fig. 6 is a view in side elevation of' -theoptical system shown in Fig.

Fig. 'l is a view in perspective showing "the essential elements of the. optical system shownin Fig. 5;

Fig. 8'--is a detail view in perspective showing the essential elements of the indicator utilized in the practice of my invention;

Fig. 9 is a view in perspective showing a portion of an aperture plate utilized in the practice of my invention;

Fig. 10 is a view in front elevation showing a photo-sensitive system constructed in accordance with my invention;

Fig. 11 is a view in side elevation of the photosensitive assembly shown in Fig. 10;

Fig. 12 is a diagrammatic view showing the circuit of the photo-sensitive device and its associated amplifying elements that is utilized in the practice of my invention.

The apparatus shown in Fig. 1 comprises a lathe l incorporating the usual elements, to-wit, a support 3 for a cutting tool 5 and a suppor I for a work-piece (not shown), to be shaped in a predetermined manner. The cutting-tool support 3 is equipped with the ordinary adjustments and is motivated by a motor (not shown), through a system of clutches and gears in a manner depending on the disposition and the desired structure of the piece to be shaped. The motor and its coupling do not concern the present invention and are for this reason not shown.

The cutting-tool support 3 is equipped with a slotted extension 9 in which a bracket II is .ad-

justably secured. A container l3 having disposed therein the elements of the optical system, which will be described in detail hereinafter, is secured to an upper flange I5 of the bracket ll while a container H, in which a photo-sensitive device I9 and certain amplifying elements 21 also to be described in detail hereinafter are disposed, is secured on a lower flange 23 of the bracket H. A beam of radiant energy is projected through an opening in the container I3 of the optical system and passes through an opening 25 in the container 23 of the photo-sensitive system, thereby energizing the photo-sensitive to be motivated is dependent on the particular machine utilized and should be apparent to one skilled in the art and desiring to apply my invention to a particular machine. To discuss the manner in which the machine is operated from the clutches would, therefore, be superfluous in the present state of the art, and would render the specification unnecessarily verbose.

It is to be noted that since the containers l3 and i1 for the optical system and for the photosensitive system are both secured to the tool support 3, they are therefore movable therewith and follow the motion of the tool 5.

A template 39 of structure corresponding to the shape of the work-piece that is desired is secured to a clamp 4| suitably mounted in a vise 43 which in turn is slidably supported in a track 45 secured to the lathe I and is thus capable of proper positioning in the lathe. ,When properly positioned the template 39 is so oriented that its edge 41 that is so cut as to correspond to the desired final configuration of the work-piece, intercepts or partially intercepts the beam of radiations projected from the container |3 for the optical system. The movement of the tool support 3 and, therefore, of the tool 5, is predetermined by the extent to which the beam of light is intercepted by the edge 41 of the template 39. The beam of light is movable relative to the template 39 and it is, therefore, capable of tracing out in space a cylinder corresponding to the edge 41 of the template 39. The interaction between the beam, the photo-sensitive system and the template 39 is such that substantially such a cylinder is traced. At the same time the cutting edge 49 of the tool 5 which moves with the beam of radiations traces a curve corresponding to the configuration of the guiding edge 41 of the template 39 and when in engagement with the workpiece shapes the latter to correspond to this configuration. I

The template 39 is of such structure that projecting portions of its controlling edge 41 correspond to the indentations to be milled on the work-piece and the indentations of its controlling edge correspond to the projections in the final work-piece. This procedure is followed since to provide for the accurate correspondence of the movement of the cutting-tool 5 with the movement of the light beam. For proper operation of the system the light beam should cut the same configuration in space as the cutting-tool 5 cuts out in the Work-piece. It is to be noted that the template is of such structure that it may be utilized as a finish gauge for the work-piece.

In accordance with the practice of my invention, the movement of the light beam and its attached elements is dependent on the state of excitation of the photo-sensitive device l9 and the circuit associated with the photo-sensitive device I9 is so adjusted that the cutting-tool 5 is moved in an inward direction when the beam of light is totally obstructed and is moved in an outward direction when the total radiant flux impinging on the photo-sensitive device I9 is greater than a predetermined value. On the other hand, when a predetermined minimum radiant flux is less than the predetermined value projected on the photo-sensitive device i9, the tool 5 is moved neither in nor out but in a direction transverse to the work-piece.

The operation of the system can probably best be explained with reference to the central projection 5| of the template 39 shown in Fig. 1. Assume for example that the beam of light is totally obstructed near the inside terminal 53 of the central projection 5|, and that when moving transverse to the work-piece it moves in a direction away from the plane of the drawings. The tool 5 will then move in an inward direction and the beam of radiant energy will be gradually displaced relative to the template 39 in such manner that a small amount of radiant energy is ultimately projected over the edge 41 of the template onto the photo-sensitive device i9. As soon as the necessary minimum flux impinges on the photo-sensitive device l9, the photo-sensitive system is so actuated that the inward motion is arrested, while the transverse motion is initiated. Asthe tool 5 is therefore moved in a transverse direction, the beam of light is again obstructed completely, the necessary relays of the photosensitive system are again actuated and the transverse motion is stopped, while the inward motion is again initiated. The same process is repeated until the tool 5 attains such a position that the beam of light is obstructed by the region of the stationary point 55 of the central projection 5| of the template 39.

At this point, the inward motion is again stopped and the transverse motion is again initiated. However, by reason of the fact that the side of the projection towards which the beam of light is now moved slopes in a direction opposite to the direction in which the other side slopes, the flux impinging on the photo-sensitive device I9 is increased by the transverse motion of the tool 5 rather than decreased. For this reason,.the flux impinging on the photo-sensitive device |9 soon attains a value for which the transverse motion is stopped and outward motion is initiated. By reason of the outward movement of the beam of light relative to the template 31, the total flux projected on the photo-sensitive device is now decreased until the minimum value is attained for which the outward motion is arrested and the transverse motion is again initiated. This process is repeated until the beam of light is obstructed by the region adjacent the outer stationary point 41 of the projection 5|. At this point the beam of radiant energy begins to climb up on the successive projection 59 of the template 39 and the tool begins to move correspondingly.

It will be noted that in operation the radiant beam of the pick-up element moves along the edge of the template 31 in small steps, corresponding to the motion of the tool. That is to say, the path of the pick-up element is made up of a series of short straight lines, each straight line at right angles to the successive straight line and the whole series of straight lines tracing out a curve corresponding to the edge of the template.

The image 6| that is projected on the template 39 by the light beam is substantially identical in form to the configuration of the cutting edge 49 of the cutting tool 5. In general, the

cutting edge 49 is of circular form and the image is correspondingly of circular form, the diameter of the beam being substantially equal to the diameter of the cutting edge 49 of the tool 5. This condition is necessary to eliminate difliculties which might otherwise arise in cutting corners.

In Figs. 2, 3 and 4, the difliculties which arise in cutting a turn or a corner in the work-piece are illustrated diagrammatically. In Fig. 2, a portion of the guiding edge 41 of the template 39 is shown and an image 63 of a light source having a diameter smaller than the diameter of the cutting edge 49 of the cutting-tool 5 is shown as impinging on the edge 41 in two successive regions. As the light beam moves relative to the template 39, the image moves out along the curve 41.

In Fig. 3 a corresponding portion of the workpiece 55 is shown in its desired configuration and two posiitons which the tool 5 assumes relative thereto are shown. The positions correthe assembly comprising the source 81 the con-.

spond to the positions of the image 63. It will be noted that the image 63 and the tool are shown in Figs. 2 and 3 as having moved from a rectilinear portion of the template and work pin adjacent to a curved portion, to the curved portion. In the first of these positions the template 39 obstructs the beam while in the second of these positions, the beam projects over the edge 41 of the template since the direction of motion of the tool is not altered until suiiicient radiant energy is projected over the edge t! of the template 39 to suitably energize the Photosensitive device. The tools project over the desired edge of the work-piece 65 in its displaced position. If, therefore, the image 63 is of smaller diameter than the cutting edge 49 of the tool 5, the contour which the tool will follow, will correspond to the envelope of a series of tool positions represented by the tool shown in Fig. 3

and, will not correspond accurately to the configuration of the template 39. A corresponding discrepancy occurs if the image 83 is of larger diameter than the cutting edge 430i the tool 5.

In Fig. 4, a section of the template 3!! is shown as it appears when intersected by an image, the diameter of which is equal to the diameter of the cutting edge 49 of the tool 5. As will be noted in comparing this view with Fig. 3, the movement of the tool is controlled by the periphery of the image and when the periphery of the image projects over the template 39 by a predetermined amount, the direction of motion of the cutting tool is properly adjusted. Thus, before the cutting tool can be projected to such an extent as to materially vary the configuration of the workpiece from that desired, its direction of motion is changed by reason of the fact that sufilcient light is projected over the edge M of the template 39 to properly energize the photo-sensitive system. The cutting tool 5, therefore, accurately follows the contour of the template 33 and the final configuration of the work-piece accurately corresponds to the contour of the determining edge W of the template.

The cutting tools utilized in the practice of my invention are not of the some diameter and as a matter of fact, vary widely in diameter. I have, therefore, been confronted with the problem of providing an optical system for so varying the diameter of the cross section of the light beam that my invention can be practiced with cutting tools of widely diverse dimensions.

The optical system provided in accordance with this feature of my invention is shown in detail in Figs. 5 to 9, inclusive. As can be seen from these views, it comprises essentially a light source 61 preferably an incandescent lamp, with a small filament69, a condensing lens II, and aperture plate I3 of suitable character and a projection lens I I whereby the image of an illuminated aperture I5 in the aperture plate is projected on the template 39. The condensing lens II and the aperture plate I3 are secured to a bracket I1 and the source 61 is supported on a projection I9 of the bracket II. The bracket TI, is, in turn, equipped with ears 8i that are engaged by the terminals of a bow spring 82 the face of which engage one rail of a track 83. The bracket 11 is thus held in slidable engagement with the track 83. The bracket 11 is moreover maintained on the track 83 by a plurality of plates 85 which are secured to the track 83 and project over the sides thereof to engage the projecting ears 8| of the bracket 11. It is seen that, as the bracket I1 is moved along the track 83, the position of by a plurality of plates 93 that are secured to the track 85 and engage the ears 9| projecting laterally from it.

The lamp assembly and the imaging lens as-, sembly are moved relative to each other and relative to the template 39 by the engagement of the projecting ends 95 and 91 of a plurality of rods 99 and I III secured to the brackets 11 and 81, with a plurality of cooperating cams I03 and I05 of suitable structure. Each 01' the cams I83 and I05 is milled in a block Ill! and I03 and the blocks are mounted on a plate It I which may be rotated manually from a knob H3 through a system of gears H5. As theplate III is rotated, the position of the pins or cam followers 33 and I III, in engagement with the cams I03 and I05 is changed and the position of the supporting brackets Ill and 8! for the lamp assembly and for the lens assembly are correspondingly changed. It is to be noted that as the positions of the aperture plate I3 and of the projecting lens It are changed relative to the template 39, the dimensions oi the image projected on the template are changed and the system is thereby adapted to be utilized with cutting tools .5 of diflerent dimensions.

The cam plate III may be locked in any one of a plurality of positions by the engagement or a slotted stud member I which screws into the track 83, with a disc sector H9 which is mounted on the shaft II of the cam plate III. The locking stud III is equipped with a suitable handle I23 which renders it capable of being easily manipulated.

.The aperture-plates I3 are substantially rectangular and each plate is equipped with four holes I25 so milled that the lines drawn through their centers would form a square on the corners of which the centers are disposed. The holes are normally traversed by a plurality of studs I2'I whereby the plates I3 are supported. Apertures I5 of diiferent diameters are drilled substantially midway between the supporting holes I25 and as will be apparent, the particular aperture I5 that is utilized at any particular time is dependent on the orientation of the aperture plate 13 in ferred to maintain the apertures I5 of diameters,

that are multiplied by two of each other, the smallest aperture I5 having a diameter that is of the diameter of the largest aperture on any particular plate I3. It is seen that by utilizing a single plate I3 in its various possible orientations and in addition by applying the adjustments provided in the system, the system is adapted to be utilized with a wide variety of cutting tools 5. However, in the practice of my invention, I have found it necessary to utilize three aperture plates rather than a single plate. Two of these plates are ordinarily supported in a storing position as shall be described hereinafter while one plate is supported in operative position.

It is essential that the optical system be provided with a calibrated scale for indicating the diameter of the aperture image corresponding to to the various positions of the adjusting knob H3, and the provision of such a scale for the numerous apertures raised -a considerable problem. The scale constructed in accordance with my invention comprises a plate I29 having series of dials I3I, I33 and I35 ruled thereon. The plate I29 is mounted concentrically with the knob II3 whereby the cam plate III is rotated.

Each dial I3I, I33 and I35 is calibrated to read the dimensions of the image of the largest aperture 15 of a single aperture plate 13. The image dimension which corresponds to a particular set ting of a dial when the aperture plate 13 is so oriented that any other aperture when the smallest one is being projected on the template 39' may be obtained simply by dividing the reading of dial by 2, 4 or 8 depending on the particular aperture utilized. Y

The indicating disk "I29 may be observed through an opening I31 in the container I3 of the optical system and. the particular dial I3I, I33 or I35 corresponding to the plate 13 which is in operative position is visible through the opening while the other dials are covered by the sides oi. the aperture plates 13 which are not being utilized and which are, therefore, supported in storing position adjacent to the dial disk I29.

To provide for the exposure to view of the proper dial, the aperture plates 13 are, equipped with slots I39. The slots I39 in one plate are so positioned that the two upper dials I3I and I 33 are visible through the plate 13 when the plate is mounted in storing position, the slots I39 in the second plates 13 are so positioned that the lower two scales I 33 and I35 are visible through the plate when it is mounted in storing position and the slots I39 in the third plate 13 are so positioned that the upper and lower scales I3I and I35 are visible through it while the central scale is covered when it is mounted in storing position. When two of the plates 13 are superposed upon each other in storing position, only one of the dials I3I, I33 or I35 remains visible through the superposed plates and this dial corresponds to the particular aperture plate 13that scale is covered; the central scale I33 must correspond to the plate 13 in which the slots I39 are so cut as to leave exposed to view the upper and lower scales I3I and I35 and the lower scale I35 corresponds to the plate 13 in which the slots I39 are so cut as to leave exposed to view the upper and central scale I3I and I33.

The utilization of the optical system is apparent from the above description. The particular plate 13 to be utilized is mounted on the position provided therefor on the bracket 11 while the other plates 13 are mounted in storing position. The hand knob H3 is then turned until the proper scale indicates the diameter of the cutting edge 49 of the tool that is to be utilized and the system is then locked in position. In its locked position, the optical system is thus adapted to be utilized with the tool for which it was thus adjusted.

The photo-sensitive unit is shown in detail in Figs. 10 and 11. As shown in these views, the unit comprises in addition to the photo-sensitive device I9, a light chopper Ill that is rotated from a motor I 43 of suitable character and is so mounted within the casing I1 that its teeth I45 interrupt the light which is projected through theopening 25 on the cathode I41 of the photosensitive device I9. The light thus interrupted excites the photo-sensitive device I9 and the output of the photo-sensitive device is amplified by a plurality of high vacuum amplifiers 2|, I5I, I53 and I55; the first one 2|, of which is mounted contiguous to the photosensitive device I9 to eliminate any dlificulties which might otherwise arise from capacity losses inherent in long leads extending from the photo-sensitive device to the amplifier 2|. Suitable partitions I59 are pro vided in the container I1 to isolate the photosensitive device I9 from the amplifier 2| and from the other elements of the system.

The complete amplifier that is preferably utilized in the practice of my invention is shown in detail in Fig. 1 2 and includes in addition to the high vacuum amplifiers 2I, I5I, I53 and I55. The resistors I6I, I53 and I55 and the capacitors I61, I59 and HI whereby the amplifiers are coupled to each other. The last amplifier I55 is coupled to a gas filled electric discharge device I13 preferably of the grid glow type through a capacitor I15 and a resistor I11 and its output potential is impressed between the control electrode I19 and the cathode I8I of the device I13.

When the flux impinging on the photo-sensitive device I9 attains a value which is determined by the setting of a potentiometer I82 coupled to the control electrode I19 of the gas-filled device I13, the device becomes energized and current is transmitted between the cathode II and the anode I83 thereof.

However, the capacitor I85 of suitable magnitude to correspond to the output of gas-filled device I13 is connected in series with its principal electrodes I8I and I83 and as current is transmitted through the device, the capacitor I85 is charged and eventually a potential of such polarity as to oppose the current between the principal electrodes I8I and I83 of the device H3 is impressed on its plates and the device becomes deenergized. Before this condition occurs, a second gas-filled electric discharge device I91 is energized by reason of the change in potential impressed between its cathode I89 and its control electrode I9I by the current flow through the first electric discharge device I13. The second gas-filled device I91 is coupled to the first device I13ythrough a capacitor I93 of suitable magnitude and through a resistor I95, and these elements are so adjusted that, regardless of variations introduced in the characteristics of the second device I81 by aging, the excitation of the first device I13 produces sufiicient change in potential to energize the second device.

The principal circuit of the second electric discharge device I81 is connected through the exciting coil 21 of the relay 33 and when this device becomes energized the relay 33 beoomes excited and its movable contactor I 91 is disengaged from a plurality of corresponding fixed contacts I99 and engages another set of fixed contacts 2III. By the disengagement of the movable contactor I91 from the first set of fixed contacts I99, the clutches (not shown) whereby the inward or outward feed of the motor was maintained is rendered inoperative and by the engagement of the movable contactor I 91 with a second set of fixed contacts 20 I the traverse feed is initiated.

It is seen that the system involving the gasfilled electric discharge devices I13 and I 81 is so current for any appreciable length of time and has therefore, generally a characteristic which may be depended upon to remain unchanged. The second device Won the other hand, while it must of necessity remain energized for considerable periods of time, is not dependent upon its excitation for small changes in the potentials impressed on the control circuit thereof but de-' pends for its excitation simply on the potentials impressed by the comparatively large change which occurs when the-first electric discharge device I13 passes from a deenergized condition to an energized condition. The difliculties with aging which I have observed and which I have encountered in utilizing gas-filled electric-discharge devices are thus avoided and the frequent replacements or changes in the circuit which would otherwise be necessary are obviated.

The system is supplied with power from a transformer 205 through a rectifier 201 and av system of filters 209. It is a well known fact that a gas-filled electric-discharge device when once energized by a variation of the potential applied to its control circuit remains in its energized condition. regardless of the changes introduced in the potential of the control circuit until the potential between the principal electrodes is re duced to a value smaller than the value of the cathode drop of potential required to maintain the device in energized condition. Since the system in the present case is operated by direct current power supply, it is essential that some external means be provided for maintaining the gas-filled electric-discharge device in a condition continuously responsive to the variation in potential applied to the control electrodes thereof.

For this purpose,interrupters 2i I, 2I3 and 2I5 are provided. One interrupter 2 is coupled across the capacitor I whereby the first electric discharge device I13 is deenergized and it short circuits the capacitor I85 at a rate which is large compared to the rate at which changes occur in the radiant flux projected on the photo-sensitive device I9 by reason of the cooperation of the light beam and the template 39. It is seen that the interrupter 2H continues to maintain, the capacitor in discharged condition and the electrio-discharge device I13 associated with the capacitor I85 is maintained in a condition such that its control circuit is always responsive to the state of excitation of the photo-sensitive device l9.

The potential applied to the principal circuit of the second electric-discharge device it? is periodically reduced by an interrupter 2I3 com prising a rotating disk 2II equipped with insulating inserts 2I9.- The disk ZII is rotated at such a rate that the circuit is broken by the inserts at a frequency that is great compared to the rate at which the fiux impinging on the photo-sensitivedevice I9 is changed by the template 39. This circuit is, therefore, also maintained continuously responsive to the condition of the photo-sensitive device I9.

It is seen that by the action of the interrupter. 2 the first electric-discharge device I13 will be energized and de-energized continuously as long as the flux impinging on the photo-sensitive device I9 is equivalent to the necessary predetermined value. On the other hand, the changes occurring in this device will also maintain the second device I81 energized as long as the proper condition of excitation exists in the photo-sensitive device. The relay 33 associated with the second electric-discharge device I81 is, of such character that it does not become deenergized when the electric-discharge device is for an instant deenergized by the rotation of the switch 2I3. On the other hand, if after the switch 2I3 has broken the principal circuit of the second electric-discharge device IBI, the first electric discharge device I13 does not become energized for a considerable period of time, the second de vice I81 will also remain deenergized and the relay 33 associated therewith will be deenergized.

When the flux of the radiations impinging on the photo-sensitive device I9 become greater by a predetermined amount than the minimum value for which the first set of electric-discharge devices I13 and I8! become energized, the electricdischarge devices MI and 223 of a second set becomes energized. The fiux for which the devices 22I and 223 become energized is regulated by the setting of a second potentiometer 225 associated with the first device 22i of this set that is similar to the corresponding potentiometer I82 which is associated with the first device I13 of the set which has been described hereinabove. The operation of the devices HI and 223 is similar to the operation of the other set. When the second device 223 of the set becomes energized, the re-.

lay 35 is excited and the necessary clutch for producing the inward movement of the tool 5 is rendered operative, while the clutch for producing the traverse motion of the tool 5 is rendered inoperative.

A third set of devices 22? and 229 similar to thefirst two sets are provided for the purpose of stopping the machine when the excitation of the photo-sensitive device i9 is greater by a predetermined amount than the excitation necessary for energizing the second set of electric-discharge devices 22I and 223. The third set of devices is provided for the purpose of stopping the machine in contingencies or when the tool support is in such a position that the beam of light has just passed over a terminal of the determining edge M of the template 39. The exciting coil 3| of the relay 31 whereby all the circuits are opened is connected in the principal circuit of the second electric-discharge device 223 of this set.

The explanation of the operation of the relay system shown in Fig. 12, has been given in detail hereinabove. When the template 39 and optical system are so disposed relative to each other that the photo-sensitive device I9 is substantially deenergized, the controlling relays are in the positions shown in the view and the tool 5 is being fed in an inward direction. When the flux impinging on the photo-sensitive device I9 is of such magnitude that the first set of electricdischarge devices I13 and i8? are energized, the corresponding relay 33 is'energized and the inward feeding of the tool 5 is arrested while the traverse feed is initiated. On the other hand, when the light fiux impinging on the photosensitive device I9 is such that both the first and second set of gas-filled electric-discharge devices are energized, the corresponding relays 33 and 35 are in excited condition and the traverse feed is interrupted while the out-feed is initiated. correspondingly, when the flux impinging on the photo-sensitive device I9 is such that the third set of electric-discharge devices 221 and 229 are energized, the movement of the tool 5 is entirely interrupted.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention therefore, is not to be restricted, except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In a control system for a machine of the type including means for supporting a work piece and means for supporting a cutting tool to engage said work piece to shape it; a template corresponding to the desired configuration of said work piece and means for projecting a beam of radiant energy on said template, said radiantenergy projecting means comprising an aperture, means for illuminating said aperture, means for converging the rays emitted by said aperture on said template and means for varying the position of both said imaging means and said aperture to vary the dimensions of the image of said aperture on said template to correspond to the dimensions of the cutting edge of said tool. 2. In a control system for a machine of the type including means for supporting a work piece and means for supporting a cutting tool to engage said work piece to shape it; a template corresponding to the desired configuration of said work piece and means for projecting a beam of radiant energy on said template, said radiantenergy projecting means comprising an aperture, means for illuminating said aperture, means for converging the rays emitted by said aperture on said template and means for varying the dimensions of the image of said aperture converged on said template to correspond to the cutting edge of said tool.

3. In a control system for a machine of the type including means for supporting a work piece and means for supporting a cutting tool to engage said work piece to shape it; a template corresponding to the desired shape of said work piece,-means for projecting a beam of radiant energy on said template and means for varying the dimensions of said beam to correspond to the cutting edge of said tool, said varying means including an aperture plate having a plurality of apertures milled therein and spaced from each other in a predetermined manner, means for illuminating an aperture of said aperture plate, means for projecting the image of said illuminated aperture on said template and means for so orienting said aperture plate relative to said illuminating means and said projecting means that the aperture illuminated and imaged on said template corresponds .in dimensions to the cutting edge of said tool.

4. Optical apparatus comprising an aperture plate, means for illuminating said aperture plate, means for supporting said aperture plate adjacent to said illuminating means, means for projecting an image of said aperture plate on a predetermined plane, means for supporting said projecting means and means for simultaneously moving said supporting means for said projecting means and said aperture plate to vary the dimensions of the image projected on said plane.

5. Optical apparatus comprising an aperture plate, means for illuminating said aperture plate, means for supporting said aperture plate adjacent to said illuminating means, means for projecting an image of said aperture plate on a predetermined plane, means for supporting said projecting means, means for simultaneously moving said supporting means for said projecting means and said aperture plate to vary the dimensions of the image projected on said plane and means for locking said supporting means for said projecting means and said aperture plate in any one of a plurality of positions.

6. Optical apparatus comprising an aperture plate, means for projecting a beam of radiant energy on said aperture plate, means for supporting said aperture plate adjacent to said projecting means, means for converging the rays emitted by said aperture plate on a predetermined plane, means, for supporting said converging means, a cam disposed adjacent to each oi'said supporting means and means including cam followers secured to each of said supporting means and in cooperative engagementwith said cams for moving said supporting means to vary the dimensions of the image converged on said plane.

'7. Optical apparatus comprising an aperture plate, means for projecting a beam of radiant energy on said aperture plate, means for supporting said aperture plate adjacent to said projecting means, means for converging the rays emitted by said aperture plate on a predetermined plane, means for supporting said converging means, a cam disposed adjacent to each of said supporting means, dentate means for motivating said cams and means, including cam followers secured to each of said supporting means and in cooperative engagement with said cams for moving said supporting means to vary the dimensions of the image converged on said plane when said cams are motivated by said motivating means. v

K 8. In a control system for a machine of the type including means for supporting a work piece and means for supporting a cutting tool'to engage said work piece to shape it, in combination with a template corresponding to the desired configuration of said work piece, means for projecting a beam of radiant energy on said template and means for determining the dimensions of the beam projected on said template," said means including a plurality of aperture plates each plate having a series of apertures therein and means for mounting at least one of said plates in operative position; a plurality of indicating dials to correspond to the aperture plates and means for so mounting said plates in storing position that all of the indicating dials except the one corresponding to the plate mounted in operative position are covered by said plates.

9. In a control system for a machine of the type including means for supporting a work piece and means for supporting a cutting tool to engage said work piece to shape it, in combination with a template corresponding to the desired configuration of said work piece, means for projecting a beam of radiant energy on said template and means for determining the dimensions of the beam projected in said template, said means including a plurality .of aperture plates each plate having a series of apertures therein and a slot in a predetermined, region thereof and means for mounting at least one of said plates in operative position; a plurality of indicating dials to correspond to the aperture plates and means for so mountingsaid plates in storing position that the slots in each of said plates co operate to expose only the dial corresponding to the plate mounted in operative position and to cover all other dials.

10. In a control system for a machine of the type including means for supporting a work piece to be shaped, means for supporting a tool for engaging said work piece to shape it and means for motivating said tool supporting means; a template, a contour of which corresponds to the desired shape of said work piece, means for projecting a beam of radiant energy on said template, means to respond to the resultant radiant energy emitted by said template when said radiant energy isof a-total flux greater than a predetermined value for energizing said motivating means to' move said tool supporting means in a predetermined'direction and additional means to respond to the resultant radiant energy emitted by said template when said radiant'energy is of a total flux less than a predetermined value for energizing said motivating means to move said tool-supporting means in another direction.

ii. In a control system for a machine oi the type including means for supporting a work piece to be shaped, means for supporting atool for energizing said work piece to shape it and means for motivating said tool supporting means; a template, a contour of which corresponds to the desired shape of said work piece, means for projecting a beam of radiant energy on said template, means to respond to the resultant radiant energy emitted by said template when said radiant energy is of a predetermined total flux to energize said motivating means to move said supporting means parallel to said work piece, means to respond to the resultant radiant energy emitted by said template when said radiant energy is of a total flux greater than said predetermined flux for energizing said motivating means to move said tool supporting means in a direction normal to said work piece and means to respond to the radiant energy emitted by said template when it is 01' a total flux less than said predetermined flux for energizing said motivating means to move said tool-supporting means 4'0in a direction normal to said work piece and in a sense opposite to the sense in which it is moved when said total radiant flux is greater than said predetermined value.

12. In a control system for a machine ofthe type including means for supporting a work piece to be shaped, means for supporting a tool for engaging said workpiece to shape it and means for motivating said tool supporting 'means; a template, a contour-oi which correing means to move said tool supporting means in a direction normal to said work piece and means to respond to the radiant energy emitted by said template when it is' oi a total flux less than said predetermined flux for energizing said motivating means to move said tool-supporting means in a direction normal to said work piece and in a sense opposite to the sense in which it is moved when said total radiant flux is greater than said predetermined value and means for deenergizing said motivating means when the 13. In a control system for a machine of the type including means for supporting a work piece to be shaped, means for supporting a tool to engage said work piece to shape it and means for motivating said tool-supporting means; a template, a contour of which corresponds to the desired shape of said work piece, means for projecting a beam of radiant energy on said template, means to respond to the radiations emitted by said template and including a normally deen'ergized electric-dischage device and means for energizing said device, when the radiant flux emitted by said template attains a predetermined value, to energize said motivating means to move said tool-supporting means in one direction and additional means to respond to the radiations emitted by said template and including another normally deenergized electric-discharge device and means for energizing said device when the cluding means for supporting a work piece to be shaped, means for supporting a tool and means for motivating said tool-support to move said tool in engagement with said work piece thereby to shape said work piece; a finish gauge for said work piece and means, cooperating with said finish gauge as a template for controlling the motion of said tool support thereby to provide for the proper shaping of said work p ece.

15. In a control system for a machine of the type described including means for supporting a work piece and means for supporting a cutting tool to engage said work piece to shape it; a'

templet corresponding to the desired shape 01' said work piece, means for-projecting a beam of radiantenergy on said templet, meansior projecting an imagevof said'illuminated aperture on said templet and means for so orienting said aperturerelative to said illuminating means and said projecting means that the aperture illuminated on said templet'corresponds'to the dimen- .slons of the cutting edge of said tool and electrlcal control meansior controlling the position of the tool in response to the position of-the radiant energy with reference to the templet. THOMAS H. LONG. 

